> Providers can either host themselves
Outside of China, it is de facto a Google thing due to Jibe not really in mood to interconnect with others, plus the fact that Google actually shoehorns RCS in countries where they think they can get away with it. Your statement "iPhone depends on the provider so has less coverage" basically bares this one. Two example:
1. Japan has already a different provider-supported thing +Message, (RCS-based but a different flavor because RCS is complicated), but Google is trying to win to them (and if I remember correctly, au actually jumped ship to Jibe recently-ish).
2. African carriers were confused because of RCS shoehorning without the carrier's consent: SMS reliably actually decreased because Google assumes that once you got an Android phone, surely you won't temporarily use that SIM on a "basic" phone for just an hour or two, right? Google just assumes that's offline, but for people still using their Android devices to reach their family on a farm who temporarily switched to a basic phone for its reliability and reach, their messages will still be send solely via RCS (which predictably won't reach the intended recipient because, of course, it does not have RCS).
Apple of course has its incentive to keep its users on iMessage, but it now accepts RCS (whether Jibe or not) and being "patchy" means that there are many, many carriers which did not implement RCS on their volition. I just imagine how would Google handle an oppressive government's request for interception on Jibe after carriers demonstrably shown that RCS was implemented without their consent, with fines and possibly prison sentences for illegally operating a carrier service to boot.
Re: lawful interception, when carriers switch to IMS registration (as required by Apple) they should also get access to Jibe's standardized API for law enforcement tools (there's a spec for that, I forgot its name). However, just the fact RCS payloads are E2EE in Android-to-Android communications (and soon Android-to-iOS too, hopefully) might already be illegal in some places.
Google flip-flopping around its mobile IM strategy for a decade and then around carriers with RCS is getting harder and harder to understand. Pulling the rug under carriers in developing countries, who weren't interested in the drug dealer marketing tactics, is only going to solidify Meta's dominance, as doing business with WhatsApp has proven to be a much safer and saner bet all along.
> plus the fact that Google actually shoehorns RCS in countries where they think they can get away with it.
This is the real thing that nails down "RCS" as a totally google thing. Google will forcefully enable RCS for people on carriers that want nothing to do with it. And in that case Google controls the entire process every single step of the way.